Copper Triflate Catalyzed Regioselective Alkylation of Pyrrole: Conversion of 2-Alkylated Pyrroles to Novel Pyrrolizine Derivatives by Self-Cyclization

Abstract

Metal triflate catalyzed addition reaction of pyrrole to methyl 2-oxo-4-phenylbut-3-enoate and substituted derivatives generated the related novel alkylated pyrroles regioselectively at C(2) of pyrrole.Among the studied metal triflates, Cu(OTf) 2 was found to be more effective in the addition reaction.The synthesized methyl 2-oxo-4-phenyl-4-(1H-pyrrole-2-yl)butanoate esters underwent self-cyclization by heating and yielded the corresponding methyl 3-hydroxy-1-phenyl-2,3-dihydro-1H-pyrrolizine-3-carboxylate and substituted derivatives.This reaction procedure allowed easy access to pyrrolizine structure in mild reaction conditions.